a) Field of the Invention
The present invention relates to a pulse tube refrigerator, its running method, and a cryogenic system using such a pulse tube refrigerator, and more particularly to a pulse tube refrigerator capable of quickly raising the temperature of a low temperature end to room temperature, its running method, and a cryogenic system using such a pulse tube refrigerator.
b) Description of the Related Art
With reference to FIGS. 8A and 8B, the structure of a conventional pulse tube refrigerator and its running method will be described.
FIG. 8A shows an example of a conventional pulse tube refrigerator. The pulse tube refrigerator has a regenerator 100 with a high temperature end 100a and a low temperature end 100b and a pulse tube 101 with a high temperature end 101a and a low temperature end 101b. The low temperature ends 100b and 101b communicate with each other via a gas flow path 102. Regenerator material is filled in the regenerator 100, and the inside of the pulse tube 101 is vacant.
A gas jet port 103a and a gas suction port 103b of a gas compressor 103 communicate with the high temperature end 100a of the regenerator 100 via respective switching valves 104 and 105. The high temperature end 101a of the pulse tube 101 is made closed. A heater 106 is installed near at the low temperature end 101b of the pulse tube 101.
Cold areas are formed at the low temperature ends 100b and 101b by alternately opening and closing the switching valves 104 and 105 to impart a pressure change to working gas at the high temperature end 100a of the regenerator 100.
In order to raise the temperature of the low temperature ends to room temperature, the pulse tube refrigerator is stopped to raise the temperature through natural heat transfer, or the low temperature ends 100b and 101b are heated by turning the heater 106 on.
FIG. 8B shows another example of a conventional pulse tube refrigerator. In place of the gas compressor 103 shown in FIG. 8A, a gas compressor 107 having only one gas jet port 107a is used. The gas compressor 107 periodically jets out and sucks gas through the gas jet port 107a. The gas jet port 107a of the gas compressor 107 communicates directly with the high temperature end 100a of the regenerator 100. The other structures are the same as those shown in FIG. 8A.
Cold areas are formed at the low temperature ends 100b and 101b by running the gas compressor 107 to impart a pressure change to working gas at the high temperature end 100a of the regenerator 100. Similar to the example shown in FIG. 8A, in order to raise the temperature of the low temperature ends to room temperature, the pulse tube refrigerator is stopped to raise the temperature through natural heat transfer, or the low temperature ends 100b and 101b are heated by turning the heater 106 on.
Raising the temperature of the cooling ends is necessary for the maintenance of the pulse tube refrigerator, for the replacement of a material to be cooled, and for other purposes. It takes a long time to raise the temperature to room temperature through natural heat transfer so that an operation rate of the pulse tube refrigerator lowers and a manufacture cost rises.
Although it takes a relatively short time to raise the temperature to room temperature by forcibly heating the refrigerator with a heater, it is necessary to additionally prepare the heater, a heater power source, a heater controller and the like, so that the whole system of the refrigerator becomes complicated and the manufacture cost rises.